Although applicable in principle in and for any wired test system, the present invention and its underlying problem will be hereinafter described in combination with measuring signals on a bidirectional transmission line between two transceivers.
Transceivers may be connected by a bidirectional transmission line. In such a case, a first transceiver may transmit a first signal to a second transceiver via a wired transmission line. The same wired transmission line may be also used for transmitting signals from the second transceiver to the first transceiver. In case someone wishes to extract a signal which is transmitted from the first transceiver to the second transceiver, or alternatively a signal which is transmitted from the second transceiver to the first transceiver, a directional coupler has to be physically inserted into the wired transmission channel between the first and the second transceiver. Such a directional coupler allows to extract only signals which pass through the coupler in a first direction, while signals passing through the coupler in another direction are not extracted.
However, directional couplers are expensive and require a physical modification of the wired transmission line between the first and the second transceiver.